This invention relates to a control spool valve utilized in directing fluid to and from a work element.
A control spool valve is utilized in many applications to direct fluid to and from a work element. In some applications the excessive loads can be developed by the work element to cause excessive line pressure which results in valve spool seepage. When such seepage occurs, variations in the performance of the work element can result.
In one particular application of a control spool valve, the valve is used to control the positioning of a boom cylinder associated with an off-road vehicle such as excavators or backhoes. In this application, when the backhoe bucket is in a sustained raised position holding a load of rock, gravel, etc., within the bucket, the boom cylinder can experience an excessive down pressure which translates to the hydraulic fluid controlling the cylinder position. The corresponding spool position blocks flow within the valve. However, the excessive back pressure can cause seepage within the control valve along spool landings allowing the fluid seepage. Because of fluid seepage mainly from, the work port, the boom will experience a downed drift representing unstable and undesirable conditions.